Once again, making a system to check if the granaries are sufficient to feed the populace isn't rocket science.They have been keeping our population fed with our current policy where we store every grain. Currently, if a granary is full, we probably just build another one, meaning there is no reason to be sneaky.
If we change stuff so filling up our emergency reserves is a chore preventing people from enriching their families they will suddenly have a lot of reason to minimise the amount of "useless" grain they need store, meaning as soon as our production falls a bit the famine is going to commence way more quickly than we are used to.
I am really not confident in our kings ability to keep our reserves sufficient if our laws invite the forces of greed to fuck that stuff up.